Show off default hash values

hashtest.rb

puts "hash_without_default = Hash.new"
hash_without_default = Hash.new

print "hash_without_default[:key] # => "
puts hash_without_default[:key].inspect

print "hash_without_default[:key][:value] # => "
begin
  puts hash_without_default[:key][:value].inspect
rescue => e
  puts "error: #{e}"
end

puts
puts "-------------------------------"
puts
puts "hash_with_default = Hash.new {|h, k| h[k] = {}}"
hash_with_default = Hash.new {|h, k| h[k] = {}}

print "hash_with_default[:key] # => "
puts hash_with_default[:key].inspect

print "hash_with_default[:key][:value] # => "
begin
  puts hash_with_default[:key][:value].inspect
rescue => e
  puts "error: #{e}"
end

# $ ruby hashtest.rb
# hash_without_default = Hash.new
# hash_without_default[:key] # => nil
# hash_without_default[:key][:value] # => error: undefined method `[]' for nil:NilClass
#
# -------------------------------
#
# hash_with_default = Hash.new {|h, k| h[k] = {}}
# hash_with_default[:key] # => {}
# hash_with_default[:key][:value] # => nil
#